Some swings stop the instant they touch the ball. The arms fold, the barrel exits early, and the finish wraps up short — the hitter met the ball but never drove through it. It's one of the quieter power leaks, because the swing can look fine right up to contact and then just... quit. Line-drive power lives in the six inches after contact, and a cut-off swing skips them.
Through the ball, not around it
Picture the difference between a punch that lands on the surface and one that drives a few inches past it. Same collision point, wildly different force. The swing works the same way: your lead arm should keep extending through the ball, driving toward the pitcher, before the finish wraps up over your shoulder. That reach through the contact zone is where the barrel stays on the ball longest and where a line drive gets its carry.
A cut-off swing folds the lead arm early instead. Often it's a hitter trying to be "short and quick" who overcorrected past the point — short into the ball is great, but you still have to drive through it.
What the camera reads
Film open side and CoachVision measures your extension through the ball — how long your lead arm gets driving through contact, compared to your own arm fully straight. Around 1.0 means you're extending long through the zone; well under means the swing cut off or rolled over early. Because it's measured against your own straight arm, there's no absolute yardstick to argue with — it's calibrated to you.
It usually travels with a low finish height: a lead hand that stops down near the chest instead of wrapping up over the shoulder is the same cut-off swing seen at the other end. Two reads, one story.
The honest boundary: "contact" is your hands' speed peak, not bat-on-ball, and the camera can't see your barrel — so this is a read on how far your arm drives, not a barrel-path measurement. But the arm drive is the thing you can feel and fix.
The fix — reach through the zone
High-Tee Line Drives: a tee at the top of the zone, hit hard on a line without popping up. Hitting a high tee flush demands extension — you can't scoop or cut it off and still line it out, so the drill forces the reach through the ball. Ten balls, thinking "drive it back through the pitcher."
Top-Hand / Bottom-Hand Tee Work teaches each hand its job through contact: one-handed swings, short bat or choked grip, each hand learning to round through the ball rather than fold on it. Eight each hand.
The cue for both: "hit three balls in a row down the same line." Long through the ball, then let the finish wrap up over your shoulder on its own — you don't reach for the finish, you earn it by driving through.
Film one open-side swing, check your extension, then ten high-tee line drives a round until the swing drives through instead of quitting at the door.